The invention relates to a method for operating an internal combustion engine comprising at least one fuel injection valve for introducing fuel into a combustion chamber of the internal combustion engine, which valve is supplied with a specific current intensity using pulse-width modulation, in order to set a specific throughflow cross section of a fuel flow connection into the combustion chamber, wherein the current intensity changes between a minimum value and a maximum value. The invention also relates to an internal combustion engine.
The internal combustion engine can be configured in principle for any desired field of use. For example, it can serve to drive a motor vehicle or a utility vehicle. In particular in the case of internal combustion engines having a large cubic capacity and a large number of cylinders, for example at least eight or twelve cylinders, in particular a use of the internal combustion engine for driving a construction machine, a construction device or the like can be provided. Alternatively, the internal combustion engine can serve to drive a watercraft. The internal combustion engine is preferably a reciprocating piston engine; but of course other designs can also readily be implemented.
Each cylinder of the internal combustion engine is assigned a combustion chamber in which fuel and air, in particular a fuel/air mixture, is introduced during the operation of the internal combustion engine. Combustion of the fuel or of the corresponding mixture takes place subsequently, as a result of which a force is applied to a piston which is movably arranged in the cylinder, and consequently a torque is made available at a crankshaft of the internal combustion engine. The introduction of the fuel into the combustion chamber is carried out by means of the fuel injection valve, which can also be referred to as an injection nozzle. For example, the internal combustion engine has a storage-type injection device, which can also be referred to as a common rail injection device. In this case, the fuel injection valve is assigned to this storage-type injection device, that is to say constitutes in this respect a common rail fuel injection valve or a common rail injector.
In order to open or disconnect the fuel flow connection using the fuel injection valve, that is to say therefore to set the specific throughflow cross section of the fuel flow connection, the fuel injection valve is correspondingly actuated, in particular supplied with the specific current intensity. The actuation can take place by using pulse-width modulation in which the current intensity of the electric current flowing through the fuel injection valve changes between two values, for example between a minimum value and a maximum value. While successive actuation time periods always have the same chronological duration, the throughflow cross section is influenced by the selection of a specific duty factor. The latter indicates the proportion of the actuation time period during which the fuel injection valve is to be supplied with the maximum value of the current intensity, while during the rest of the actuation time period only the minimum value of the current intensity is present at the fuel injection valve. The minimum value is preferably zero.
However, for reasons of design, the fuel injection valve has at least one constriction, in particular in the form of a narrow gap, in the fuel flow connection of the fuel injection valve. In this constriction, particles of dirt can be deposited and coatings can form. These can lead to a malfunction of the fuel injection valve. The cylinder to which the fuel injection valve is assigned does not have any fuel fed to it in this case, or has a smaller amount of fuel fed to it than is provided for. This brings about a drop in power of the internal combustion engine and/or uneven running of the engine. In this case, the fuel injection valve must generally be replaced.
Documents DE 10 2009 029 656 A1 and DE 103 05 178 A1 are known from the prior art. The former document relates to an internal combustion engine comprising at least a first injection valve and a second injection valve, wherein each of the first and second injection valves is configured to carry out a partial stroke or a full stroke, and a control unit which is configured to actuate the injection valves individually, with the result that the first injection valve can be switched over from the partial stroke to the full stroke, in order to carry out a full stroke at least once, wherein in this context the second injection valve remains in the partial stroke. The document mentioned last presents a method for operating an injection valve of an internal combustion engine.